I must be stupid. Round of 16 means 16 players. But there already 16 seeded players. So it doesn't make sense.
Saturday: 48 players playing
Sunday: The 2 best of each group go forward --> 32 players.
On another weekend: The winner of each series comes forward --> 16 players
and so on.
The 16 seeded player will be for the 48 run on the first Saturday.
Now clear?
If not, AE will soon publish a video, where he explains the system in detail